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      The Effect of Norepinephrine on the Coronary Microcirculation

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          The role of the sympathetic nervous system in the regulation of large coronary artery tone has been well defined. Studies of adrenergic regulation of coronary-resistance vessels have largely been limited to indirect inferences based on flow measurement obtained in vivo. The purpose of the present study was to determine the effects of norepinephrine (NE) on the coronary microcirculation using direct in vitro approaches. Porcine coronary microvessels (80-200 µm in diameter) were pressurized in isolated organ chambers. Diameters were measured using a Halpern microvessel imaging apparatus. After preconstriction with leukotriene D<sub>4</sub>, NE caused complete relaxation. Relaxations to NE were inhibited by propranolol. Relaxations to NE were also inhibited by LY83583 (which depletes cGMP) and hemoglobin (which binds endothelium-derived relaxing factor, EDRF). NE caused minimal or no constriction in both preconstricted and nonpreconstricted microvessels even in the presence of hemoglobin and propranolol. In conclusion, NE predominantly dilates porcine coronary microvessels, both by β-adrenoceptor activation and by stimulating release of EDRF. There is minimal α-adrenoceptor-mediated constriction of coronary microvessels.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          23 September 2008
          : 29
          : 1
          : 2-7
          Cardiovascular Center and Veterans Administration Medical Center, Departments of Surgery and Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa, USA
          158924 J Vasc Res 1992;29:2–7
          © 1992 S. Karger AG, Basel

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          Page count
          Pages: 6
          Research Paper


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